As I am building out my pro forma, I keep running into this headache as to whether I need to incorporate sensitivity tables. 

Both are older homes, the 3/3 was renovated in the 80s.2/1 home is prime candidate for a tandem house out back or teardown and convert to Rowhome zoning, (properties were recently rezoned just across the alley tandem homes, ADU already zoned ok) 3/3 is newer, on a double lot, but my thinking is that I could hold these for a while, go through the rezoning process and sell both if/when the neighborhood continues to get hot enough for more density building, possibly work with a contractor friend of mine to get going in this direction, or try to do construction of tandem home behind 2/2 and then adu behind 3/3 home.Are there any resources for spreadsheets or analysis specifically in this realm/that I could show my financiers to calculate the projections on this?

You could buy stock in the Empire State Building, which I believe is still a single asset public REIT.  

I am looking at a mixed use building in the 6 to 12 unit range in an expensive area of the country.

And of course knowing what your costs will be to build.

I've reached out to multiple insurance companies that are saying they won't insure a building that old.

One other question that your carpenter / building department / insurance company may flag relates to the spacing between balusters, which has decreased over the years.

I did reach out to one private individual that had a building listed in my area that was of interest, and although priced right at retail the numbers that were provided were so "high level" and lacking any detail that I didnt pursue it any further.

His plan involved reframing some of the building and inhabiting illegal tenants.

The project is 1.9 million for the land and then the development of the low-income housing  you need a qualifier and a single purpose entity. we do 5-10% ownership in every deal we build so we can continue to be qualified. do you have the financial backing?